Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method of performing a hybrid automatic repeat request (HARQ) in a wireless communication system, and an apparatus using the method.
Related Art
Long term evolution (LTE)/-LTE-Advanced (LTE-A) based on 3rd generation partnership project (3GPP) technical specification (TS) releases 8-11 are widely employed mobile communication standard. Recently, next-generation mobile communication with higher efficiency is under standardization.
In a communication system, a duplex scheme includes a time division duplex (TDD) and a frequency division duplex (FDD). The TDD provides an uplink communication and a downlink communication in the same frequency band. The FDD provides the uplink communication and the downlink communication in different frequency bands.
A carrier aggregation (CA) is a technique capable of providing a plurality of component carriers to the UE. Each component carrier may be defined as one cell. When the plurality of component carriers is configured for the UE, the UE may receive services from a plurality of serving cells.
Each serving cell may be configured with the FDD or the TDD. In a carrier aggregation environment, the UE may be configured with a plurality of duplex schemes. For example, if two cells are configured for the UE, the cells may be configured as a TDD cell-TDD cell or a TDD cell-FDD cell. Accordingly, a throughput of the UE may be increased in various network environments.
However, since a plurality of duplex schemes is applied to the UE, there may be a problem in an operation for the downlink communication and the uplink communication.